Flow-solid coupling analysis of underground reinforced concrete forked pipe enclosing rock and structure

Area of Science:

• Geotechnical Engineering
• Hydrogeology
• Structural Engineering

Background:

• Designing high-head underground turnout pipes in water-rich areas presents challenges in maintaining surrounding rock stability during excavation and lining integrity during operation.
• Existing methods often do not fully account for the complex interplay between seepage, rock stress, and lining behavior.

Purpose of the Study:

• To develop and validate a coupled numerical simulation method for analyzing the stability of surrounding rock and lining structures in high-head underground turnout pipes.
• To investigate the mutual feedback effects between excavation, rock stress, seepage, and lining cracking under operational conditions.

Main Methods:

• An iterative numerical simulation method was developed to couple excavation load release, surrounding rock damage evolution, and seepage effects.
• A numerical analysis method was proposed to couple internal water seepage with lining cracking and stress damage, considering the cracking characteristics of reinforced concrete linings.
• The developed methods were applied to a specific forked pipe project for validation.

Main Results:

• During construction, coupled iterative analysis showed a significant increase in the rock's damage zone, stress, and displacement around the cavern.
• During operation, increased internal water pressure accelerated lining cracking due to external water infiltration.
• Post-internal water application, the surrounding rock primarily bears the internal water pressure, with the reinforcement handling only a portion of the circumferential force.

Conclusions:

• The proposed coupled numerical simulation method accurately captures the complex interactions affecting stability in high-head underground turnout pipes.
• The findings provide crucial theoretical support for the design and reinforcement of rock support and lining structures in similar underground engineering projects.
• The study offers significant theoretical and practical insights for addressing challenges in water-rich underground construction.